The center of the retina is anatomically identified as the macula, and in particular, the center of the macula, the area responsible for best vision, is known as the fovea. This specialized area of the retina must be disease free for optimal central vision to occur. Many different retinal diseases, for example Age Related Macular Degeneration (ARMD), can destroy the fovea and/or the surrounding macula area and thereby cause an area of blindness. This area of central blindness results in a black hole in the patient's vision known as a scotoma. Such patients will have their critical central vision severely compromised. ARMD, typically found in patients over 50 years of age, is reaching epidemic proportions. Its effects are often devastating both in terms of mobility and daily living functions. Attempts to improve levels of vision in patients with macula disease have mostly centered on methods that simply magnify the image (telescopic spectacle or handheld lenses, or simple video magnification systems), vary the image contrast or color, or attempt to displace the image with simple prisms. See U.S. Pat. No. 7,901,072 (2011) to Eagan et. al. These methods are overly simplistic and have proven to be mostly ineffective.
Retina specialists have heard from many patients and families of patients with poor central vision, “most of the time I can't see anything.” However there are moments when they, surprisingly, see a small object, such as a needle on the floor only to be frustrated, a moment later, that the same object “disappears” from view. Since the macula and fovea are damaged in these patients, it is apparent that “eccentric viewing” must somehow account for these momentary improvements in visual function. Eccentric viewing in macular disease is well known to exist, whereby the patient momentarily uses a region of peripheral healthy retina. Unfortunately, only fleeting moments of vision are realized. Even with relatively small lesions, the disease-induced destruction of the fovea results in a scotoma that prevents effective fixation (necessary to keep the eyes locked in on an object) that would keep the area of regard (AR) in view for longer periods. Each time an ARMD patient attempts to return to “find” that small object, the central scotoma prevents them from being able to regain the AR and hold it in view. Only through random body positional and/or eye movements might the object be momentarily seen again. These random retakes of the image do not provide the patient with any practical degree of visual capability.
To overcome this impaired vision, some visually-impaired people have trained themselves to view objects at an angle, e. g., by looking at things out the corner of their eye. In this way, light is introduced through the pupil at a perceptible angle. In addition, many devices and procedures have been developed with the goal of alleviating the loss of sight resulting from macular degeneration and other vision impairments.
Prism correction has been added to prescription lenses of glasses for individuals with impaired vision to direct a viewed image to functioning or preferred portions of the retina. The required prism is determined by a subjective refraction using discrete steps of prism diopter and base, and once prescribed, the prism is built into the glasses. Because it is ground into the lens of the glasses, the prism cannot be changed without reexamination and the subsequent production of new spectacles. More significantly, the prism corrected image, because of its fixed nature cannot account for patient head or eye movements and, therefore, cannot be made to consistently have an image fall upon functioning and viable retina.
Other measures for ARMD vision correction include wearable telescopic spectacles or intraocular lens implants that incorporate miniature telescopes. Telescopic methods are not a best solution because they do not redirect the image to a functioning portion of the retina, but merely enlarge the image so that more area of the retina is used to see only small fractions of an image at a time. Patients are frustrated by having to piece together these small fragments to gain perception of an area of regard (AR). Wearable telescopic spectacles are often tried initially only to end up “in the drawer”, unused. Intraocular telescopic implants are surgically invasive, oftentimes irreversible, cannot be modified or further optimized to adapt to a patient's needs. They have not gathered widespread use likely because of the same image limitations of wearable telescopes.
U.S. Pat. No. 7,901,072 provides a personal video display device. The video display device includes a wearable frame, a mount, a first prism, and a second prism. The wearable frame contains an image display displaying an image perceptible by the wearer. The mount is selectively attachable to the wearable frame. The first prism is contained in the mount and is disposed between the image display and the wearer's eye. The prism has a first surface facing the image display and a second surface angled relative to the first surface. The second prism is contained in the mount and is disposed between the first prism and the wearer's eye. The second prism has a first surface receiving the image emitted from the second surface of the first prism and a second surface angled relative to the first surface through which the image exits the second prism and is directed to the wearer's eye. The first prism and the second prism are moveable relative to each other to alter the angle at which the image exits. The second prism and is directed to the wearer's eye. Specifically, in this above cited embodiment, its design is optimized to present images to a healthy retina with normal central vision. The need exists to have an eyeglass like device that can improve vision in wearers that do not have a healthy central retina and which effectively directs images away from their scotoma to their best available portion of the remaining healthy retina.
The purpose of the present invention, the Relocated Image Virtual Retinal Display (RIVRD), is to incorporate a visual system aid whereby the AR, that portion of the central vision that could not be seen because of the scotoma, is intentionally directed away from the scotoma. The present invention is designed to persistently project or present a “relocated” image (RI) obtained by a small video camera that is capturing the AR, onto the healthiest and greatest vision potential region available on the retina. This area of remaining best vision potential, unique and different for each individual, includes a region known as the preferred retinal locus (PRL). The location of a particular patient's PRL and surrounding “best remaining vision potential” can be reproducibly discovered and mapped using microperimetry techniques (for example, via use of a scanning laser ophthalmoscope). The PRL, including nearby adjacent areas, discovered and mapped for each specific patient, will be the new discrete retinal area that will be used as the point of central fixation for relocated images (RI). That is, the AR will be transformed to an RI that will be seen via the determined PRL region which will provide improved vision to the patient. The RIVRD must be programmed for each patient, but repeat testing of hundreds of patients will likely identify a most likely PRL region for each geographic type of central scotoma (since most are centered at the fovea and mostly differ by overall diameter of involvement) thereby reducing or eliminating the need for custom design in every case.